PSA: I read that most late payments happen in the first 90 days... and I think that's wrong.

I saw a report from a small business group last week that said over 60% of overdue bills are from clients you've worked with for less than three months. It was a big number, so I checked my own records from last year. For me, the slow payers were almost all people I'd been dealing with for over six months... they just got comfortable being late. The 'new client' rule didn't hold up at all. Maybe the advice to watch new people closely lets the old, familiar ones slide. Has anyone else found their long-term clients are the ones who start to drag their feet?